1. Technical Field
The present invention relates to a battery cooling system for a vehicle, and more specifically to a cooling system for a battery mounted on an electric vehicle, a hybrid electric vehicle, and other vehicles, which use an electric motor as a drive source.
2. Related Art
Batteries for supplying electric power to an electric motor serving as a drive source in electric vehicles, hybrid electric vehicles, and so on suffer from not only deterioration of performance but also a reduction of product life when the temperature thereof rises. In order to deal with these disadvantages, a system for directing the air in a vehicle compartment which is conditioned by an air conditioner to a battery chamber by means of a cooling fan to thereby cool a battery has conventionally been proposed.
FIG. 6 illustrates a structure of a battery cooling system for a vehicle which is disclosed in JP 10-306722 A. A vehicle 10 includes a battery 12 installed therein for driving an electric motor, and an air conditioner 16 for air-conditioning the interior of a vehicle compartment 14. The battery 12 is disposed within a battery chamber 18 in which a cooling device 20 is also provided. The air conditioner 16 includes a compressor or an evaporator, and the evaporator is provided within an air conditioning duct 28. In the air-conditioning duct 28, a blower fan 34 is provided as an air blower means between the evaporator and an air inlet port, and a switching damper 36 which opens or closes the air inlet port is provided near the air inlet port. On the other hand, the battery chamber 18 is provided in a space between a rear seat back 56 and a trunk 58. One end of a cooling duct 60 having the other end opened to the interior of the vehicle compartment 14 is coupled to the battery chamber 18. A cooling fan 62 is provided within the cooling duct 60, and the conditioned air within the vehicle compartment 14 is supplied as cooling air to the interior of the battery chamber 18 by means of driving the fan motor. One end of a circulation duct 66 and one end of an exhaust duct 68 are coupled on the side of the battery chamber 18 opposite to the cooling duct 60 with the battery 12 being interposed therebetween. The other end of the circulation duct 66 communicates with the vehicle compartment 14 via the trunk 58, and the other end of the exhaust duct 68 is opened to the outside of the vehicle. A switching damper 70 is further provided between the circulation duct 66 and the exhaust duct 68, and the battery chamber 18.
The battery 12 provided within the battery chamber 18 is cooled by the air supplied from the vehicle compartment 14 by the cooling fan 62. The air, after cooling the battery 12, is returned to the vehicle compartment 14 via the circulation duct 66 in a state in which the exhaust duct 68 is closed by the switching damper 70 and is exhausted to the outside of the vehicle via the exhaust duct 68 in a state in which the circulation duct 66 is closed by the switching damper 70.
Further, JP 2004-48981 A describes control of the operation mode of a fan which cools a battery installed in a vehicle in accordance with the noise in the vehicle compartment. More specifically, JP 2004-48981 A describes that it is possible to effectively cool the battery installed in a vehicle while reducing the sensory noise sensed by a passenger of the vehicle by controlling the rotation speed of the fan at a low speed when the vehicle compartment is quiet and controlling the rotation speed of the fan at a high speed when the vehicle compartment is noisy.
As described above, when the air within the vehicle compartment 14 is directed to the battery chamber 18 by means of the cooling fan 62 to cool the battery 12, it may be difficult to effectively cool the battery 12 depending on the travelling state of the vehicle 10. Specifically, if the vehicle 10 is travelling at a certain speed with the windows of the vehicle 10 being opened, the base pressure of the inlet-side static pressure of the cooling fan 62 becomes negative pressure compared to that when the windows are closed, in accordance with the degree of window opening and the vehicle speed, and the air quantity for cooling by the cooling fan 62 is reduced. Also, when the cooling fan 62 is stopped or rotates at a low speed, there is a possibility of backflow of the air outside of the vehicle through the exhaust duct 68 in a state in which the circulation duct 66 is closed by the switching damper 70.